checkpatch: is_userspace: exclude kernel code under tools/

Patch series "checkpatch: skip more kernel-only checks for userspace code".

Commit 99b70ece33d8 ("checkpatch: suppress strscpy warnings for
userspace tools") added is_userspace() to skip checks which only make
sense for the kernel. This series extends that to a few more checks
which produce false positives for userspace code under tools/:

 - ENOSYS: the "ENOSYS means invalid syscall nr" rule is about the
   kernel ABI; in userspace, errno == ENOSYS is the standard way to
   detect a missing syscall (e.g. to skip a selftest on older kernels);
 - AVOID_BUG: "Do not crash the kernel" does not apply to userspace,
   where BUG()/BUG_ON() are assert-like shims;
 - SSCANF_TO_KSTRTO: kstrto<type> is not available in userspace.

Running "checkpatch.pl -f" (with --strict for AVOID_BUG, which is
a CHECK in file mode) on the files under tools/ that use ENOSYS, BUG()
or sscanf() gives 699 such warnings before this series (ENOSYS: 188,
AVOID_BUG: 491, SSCANF_TO_KSTRTO: 20), and none after.

Since tools/ also contains some kernel code (test modules, Kbuild-built
mocks, rvgen templates), patch 1 makes is_userspace() return false for
those locations, so they are still subject to all the kernel checks
(this also applies to the existing strcpy/strlcpy/strncpy checks).


This patch (of 4):

is_userspace() treats everything under tools/ as userspace code, and is
used to skip checks that only make sense for the kernel. However, tools/
also contains some kernel code: test modules, Kbuild-built mocks, and
templates and golden outputs of the runtime verification monitor
generator. Such code should be subject to the same checks as the rest
of the kernel.

Explicitly exclude the known locations of kernel code under tools/.

Link: https://lore.kernel.org/20261022224426.2756960-1-kolyshkin@gmail.com
Link: https://lore.kernel.org/20261022224426.2756960-2-kolyshkin@gmail.com
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 02d47e5bb5ed..0f666c15c10f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2670,6 +2670,11 @@ sub exclude_global_initialisers {
 sub is_userspace {
     my ($realfile) = @_;
 
+    # Kernel code under tools/: test modules, mocks, code generator templates.
+    return 0 if ($realfile =~ m@^tools/testing/(?:cxl|nvdimm|crypto)/@ ||
+             $realfile =~ m@^tools/testing/selftests/(?:bpf/test_kmods|livepatch/test_modules|mm/page_frag|net/bench/page_pool)/@ ||
+             $realfile =~ m@^tools/(?:power/cpupower/debug/kernel|virtio/vhost_test|verification/rvgen)/@);
+
     return $userspace if (defined $userspace);
 
     return ($realfile =~ m@^tools/@ ||